Solar panels, heat pumps and insulation in Welwyn Garden City conservation area
In the Welwyn Garden City conservation area (Welwyn Hatfield), external wall insulation needs planning permission, and so does an air source heat pump on a wall or roof facing the road; one at the back or side, internal and loft insulation and solar panels on a roof slope normally do not. The area has 11 listed buildings; on a listed building solar panels and heat pumps are not permitted development at all and need planning permission and listed building consent. 2,877 homes inside the boundary have an energy certificate: 18.3% are solid-wall homes with no wall insulation, 78.9% heat with a gas boiler and 54.3% are rated D–G; 17 have a heat pump. EPC register November 2026; rules as at 21 October 2026.
Data: EPC register November 2026 (latest certificate per home), conservation area boundaries 3 November 2026, permitted development rules as at 21 October 2026 · calculated 5 November 2026 · Methodology and sources
2,877homes with an energy certificate
18.3%solid walls, no insulation
78.9%heated by a gas boiler
17heat pumps
Article 4: Welwyn Hatfield does not publish Article 4 areas on planning.data.gov.uk — check with the council.
What needs planning permission in Welwyn Garden City
Work (house, not listed)
In a conservation area
Rule
Air source heat pump on a wall or roof facing the road, or nearer the road than the house
Planning permission needed
Part 14 Class G, G.1(j)
Air source heat pump at the back or side (outdoor unit up to 1.5 m³, MCS Planning Standards, one per house — two on a detached house)
No permission needed (permitted development), unless an Article 4 direction removes it — check with the council
Part 14 Class G
Solar panels on a pitched roof (up to 0.2 m proud, not above the ridge)
No permission needed (permitted development), unless an Article 4 direction removes it — check with the council
Part 14 Class A, A.2(c)
Solar panels on a wall, balcony or roof enclosure facing the road
Planning permission needed
Part 14 Class A, A.2(e)
Solar panels on a flat roof (up to 0.6 m above the roof)
Prior approval of appearance from the council, unless an Article 4 direction removes it — check with the council
Replacement windows and doors of similar appearance
No permission needed (permitted development), unless an Article 4 direction removes it — check with the council
Part 1 Class A, A.3(a)
Listed buildings: 11 in the area (grade I: 0, II*: 1). The table is for houses that are not listed: on a listed building, solar panels and air source heat pumps are not permitted development at all (they need planning permission), and any of these works needs listed building consent.
Flats: 35% of the certified homes here are flats or maisonettes. Homes in a block of flats have no householder rights for alterations; heat pumps and solar have their own, tighter rules for blocks of flats.
The homes in the area (latest certificate per home, n = 2,877)
Walls
Homes
Share
Cavity wall, filled
1,138
39.6%
Cavity wall, unfilled
528
18.4%
Solid wall (brick or stone), no insulation
527
18.3%
Cavity wall, insulated (as built or unspecified)
230
8.0%
Modern wall (U-value from the design)
138
4.8%
Timber frame
134
4.7%
Solid wall, internal insulation
44
1.5%
Other or not known
36
1.3%
Solid wall, insulated
34
1.2%
Solid wall, external insulation
23
0.8%
Cavity wall, partly insulated
22
0.8%
Solid wall, partly insulated
14
0.5%
Cavity wall, internal or external insulation
9
0.3%
Heating
Homes
Share
Gas boiler
2,269
78.9%
Electric (storage heaters, panels, boiler)
526
18.3%
Communal heating
58
2.0%
Heat pump
17
0.6%
Oil
5
0.2%
LPG
1
0.0%
Solid fuel (wood, coal)
1
0.0%
Loft / roof insulation
Homes
Share
No insulation
203
7.1%
Under 200 mm
1,015
35.3%
200 mm or more
797
27.7%
Insulated (depth not recorded)
214
7.4%
Flat or other home above
554
19.3%
Other
94
3.3%
Windows
Homes
Share
Double glazed
2,773
96.4%
Single glazed
52
1.8%
Secondary glazing
49
1.7%
Triple glazed
3
0.1%
CDE
Energy rating: A 3 (0.1%) · B 94 (3.3%) · C 1,217 (42.3%) · D 1,209 (42.0%) · E 305 (10.6%) · F 43 (1.5%) · G 6 (0.2%). Houses and bungalows: 65% of the homes; solar panels on 0.7% of the certificates. Most common build period on the certificates: 1930-1949. Designated: 7 October 1968.
Compared with Welwyn Hatfield and England
Share of homes
Welwyn Garden City
All 9 areas in Welwyn Hatfield
England
Solid walls, no insulation
18.3%
20.8%
48.7%
Gas boiler
78.9%
80.2%
66.4%
Rated D–G
54.3%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 59% of these are from 2020 or later (latest 29 October 2026). “No insulation (assumed)” is the assessor's default for older walls.
The rules are England's national permitted development rules (General Permitted Development Order 2015, Schedule 2, as at 21 October 2026). They do not cover building regulations or a council's own conditions. This is not a planning decision: ask Welwyn Hatfield if in doubt.
Boundary: Welwyn Hatfield Borough Council via planning.data.gov.uk (entity 44001779, reference 2714, 248.9 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.